This invention is the subject matter of Disclosure Document 070810, filed in the U.S. Patent and Trademark Office on behalf of applicant on May 1, 1978.
1. Field of the Invention
This invention relates to an improved pivotal pin and bushing joint which may be advantageously employed in a variety of hinged apparatuses, such as, for example, the endless track chain of crawler tractors, the articulated joints of lift and tilt mechanisms of loaders, and the like. More specifically, it relates to a unique cartridge-type pivotal pin and bushing joint which provides enhanced performance and more adequately copes with certain problems associated with prior art structures, particularly sealing problems.
While the present invention is described herein with reference to a particular embodiment advantageously employed in the endless track of tractors, it should be understood that the invention is not limited thereto. The cartridge-type pivotal pin and bushing joint of the present invention may be employed in a variety of forms and may be used in a variety of hinged assemblies as those skilled in the art will recognize in the light of the present disclosure.
2. Description of the Prior Art
Pivotal pin and bushing joints of the general type contemplated herein are well known in the prior art, and the seriousness of the problems associated therewith have been long recognized and have been the subject of much developmental activity. This activity is reflected in the patent art, representative patents including, for example, U.S. Pat. Nos. 2,906,562 to Burgman; 2,911,840 to Muller et al.; 3,244,457 to Ross; 3,336,089 to Krickler; 3,347,602 to Rixmann et al; 3,463,560 and 3,554,588 to Reinsma et al.; 3,574,419 to Hatch; 3,595,572 to applicant herein; 3,675,936 to Hatch; 3,680,924 to Otto et al.; 3,731,551 to Nelson; 3,759,586 to Otto et al.; 3,841,718 to Reinsma; 3,948,574 to Baylor; 3,958,836 to Brown; 3,975,028 to Satsumabayashi et al.; 3,985,366 to Plouzek; 4,007,972 to Baylor; and 4,030,730 to Maguire. The present invention is directed to improvements in such joints.
Modern-day hinged apparatuses, particularly heavy duty machines used in building and highway construction, have articulated or hinged joints which are subjected to heavy loading under extremely adverse operating conditions. The heavy loading includes operations under load on slanted surfaces and turning operations, which subject the joints to a variety of forces in various directions, including longitudinal thrust forces. The lubrication of these joints is complicated by the extremely adverse operating conditions, including widely-variable weather and temperature conditions and the inevitable presence of dirt, sand, rocks and other abrasive materials in contact with the joints and bearing surfaces under severe loading. Accordingly, it is essential that the joints be adequately lubricated and protected from abrasion by simple, reliable, effective and economic sealing means under all conditions of operation. Moreover, inasmuch as the joints are often stored for considerable periods under adverse conditions prior to installation, particularly in the field, the bearing surfaces should be sealed against rust or corrosion producing ambient conditions and the like.
The prior art solutions thereto, such as disclosed in the aforementioned patents, suffer from one or more shortcomings which limit their usefulness or effectiveness or render them problem-prone or costly. Some are inadequately lubricated or poorly sealed and fail after relatively short periods. But even it adequately lubricated, the loss of lubricant or the cost of preventing or making up for such loss make for an unsatisfactory situation. The undesired intermixing of lubricant and abrasives can cause more wear than no lubricant at all. Seals to prevent lubricant loss or the entry of contaminants are often ineffective, too complex, or too costly.
The requirement for lubricant passages and entry ports increases the cost of manufacture and requires that the design or metallurgy take in consideration the associated loss of structural strength. The provision of flowable lubricants otherwise increases the complexity of the unit when manufactured and also increases the cost of installation and periodic maintenance.
Some prior art pin and bushing joints are inherently noisy and are characterized by excessive frictional losses which require greater horsepower for satisfactory operation. The need to minimize noise pollution and to otherwise meet OSHA requirements and the emphasis on energy conservation have become major considerations in modern machinery design.
But even when prior art devices may meet operating requirements, some are too costly, or inconvenient to install and maintain. Some can not be assembled without at least one split link. Some require continued monitoring of lubricants. Moreover, some have limited shelf life in the sense that bearing surfaces thereof are subject to rust and corrosion or other deterioration prior to installation. Still other designs are not versatile in the sense that they cannot readily be used to replace other joints in the field.
Some prior art joints require manufacturing steps otherwise deleterious to the joint or materials of construction. For example, some pivotal pin and bushing joints employ a welding step during manufacture or installation. The associated heat may have deleterious metallurgical effects and may otherwise harm non-metal seals and flowable lubricants or cause the loss thereof by melting or the like.